The invention relates to a motor vehicle having a FlexRay bus and to a method for optimizing the value for at least one selected operating parameter of a FlexRay bus.
A FlexRay bus can and must have a multiplicity of operating parameters stipulated prior to said bus being started up. Furthermore, what is known as the scheduling must typically be stipulated, i.e. particular messages, which are fundamentally meant to be sent repeatedly, need to be provided for the stipulation regarding when they are sent in what form. The scheduling involves what is known as the allocation of slots to the messages. A slot is a time interval having a fixed position in time in a cycle. The allocation of the slots involves stipulating both the temporal length of the slots and the number thereof.
To date, the values for the operating parameters are stipulated totally independently of the scheduling. The parametrization is performed according to predetermined methods in which, on the basis of a particular approach, an attempt is made to guess the best parameter values. There are also separate techniques for the problem of allocating slots.
A drawback in the related art is that the opportunities provided by a FlexRay bus are not utilized in optimum fashion. The FlexRay bus systems are therefore also difficult to extend. There is a static segment having a fixed slot length and a dynamic segment having a variable slot length. The dynamic segment of the FlexRay is designed merely on the basis of a use profile in the related art, and there is no functional planning, but rather the planning is controller based.
A technical article by E. G. SCHMIDT and K. SCHMIDT (“Message Scheduling for the FlexRay Protocol: The Dynamic Segment”, IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, IEEE SERVICE CENTER, PISCATAWAY, N.J., USA, Vol. 58, No. 5, Jun. 1, 2009 (2009 Jun. 1), pages 2160-2169) describes a method for optimizing flow coordination (scheduling) for a dynamic segment for message frames of the FlexRay protocol. The method presupposes that all periodically sent messages are transmitted in static segments and the optimization is performed only for messages that are to be sent sporadically. The optimization is performed to minimize the overall length of the dynamic segment. In this case, the assurance is also provided that all messages were transmitted within their prescribed maximum transmission period. As part of the optimization, a suitable order for the transmitted messages within the dynamic segment is ascertained.
A technical article by KANG ET AL. (“A static message scheduling algorithm for reducing FlexRay network utilization”, INDUSTRIAL ELECTRONICS, 2009, ISIE 2009, IEEE INTERNATIONAL SYMPOSIUM ON, IEEE, PISCATAWAY, N.J., USA, NJ, USA, Jul. 5, 2009 (2009 Jul. 5), pages 1287-1291) describes a method for optimizing flow coordination for messages that are sent periodically on a FlexRay bus. According to the method, a split for periodically sent messages between the static segment and the dynamic segment is optimized. The optimization also comprises a combination of a plurality of messages within a FlexRay message frame.